1. Field of the Invention
Embodiments of the present invention generally relate to electrical load control of accessories in a vehicle.
2. Background Art
Keeping power losses to a minimum helps to increase fuel economy for vehicles. It is generally well known that vehicle electrical accessory devices (or loads) use a significant amount of power and that keeping power losses associated with vehicle electrical accessory usage to a minimum may increase fuel economy for a vehicle. Hybrid electric vehicles utilize a high voltage battery a fuel power engine, and regenerative braking for sources of power. Each of these sources may or may not be actively outputting power during various operating modes of the HEV. During periods of high wheel torque demand, the engine and battery may both be providing power to the wheels to meet high wheel torque demand. Any electrical accessory device that are on must continue to be powered during moments of high wheel torque demand.
Some HEVs prioritize the use of power and assign a higher priority to wheel torque over the use of power needed to drive electrical accessory devices. As a result, select electrical accessory devices may be shut down or limited for periods of time with the intent of making more power available to meet the needed wheel torque demand. Such high wheel torque demands may involve instances in which the vehicle is quickly accelerating, or when the vehicle is climbing a hill. In moments of low torque demand, the engine may generate power which may be used to charge the high voltage battery in addition to providing power to the wheels and electrical accessory devices.
In other HEV operating modes the engine is off, and stored power in the battery is used to provide power to the wheels and the electrical accessory devices. At other times, power may be generated when the vehicle performs regenerative braking. The electrical power generated from regenerative braking is also used to charge the high voltage battery and power the electrical accessory devices.
While conventional methods control the usage of electrical accessory devices without considering the source of the power being used, such an approach may not be efficient since an energy loss may be attributed to storing electrical power in the battery and then using the stored power as opposed to directly using power generated by the engine or regenerative braking.
Accordingly, it would be desirable to implement a system and method that recognizes when the vehicle is in an efficient state in order apply an increased power level to drive an accessory device, and to reduce inefficiencies associated with using stored electrical power from the battery to drive the accessory device.